BALTIMORE — According to Joe Girardi, Gary Sanchez’s strained right biceps muscle showed a bit of improvement Sunday, but nobody knows when the catcher will return from the DL.

“We’re not exactly sure how long he will be out. He feels a little bit better today, which is somewhat encouraging,’’ Girardi said of Sanchez, who had a compression sleeve on the arm in the clubhouse before Sunday’s 7-3 win over the Orioles at Camden Yards. “He’ll see our doctor [Monday] to find out what he has to do.’’

Austin Romine, who started 40 games a year ago backing up Brian McCann and Sanchez, was in the lineup against O’s lefty Wade Miley and went 1-for-3 with an RBI.

Kyle Higashioka, who spent parts of 10 years in the Yankees’ minor league system, was promoted from Triple-A Scranton/Wilkes-Barre to the big leagues for the first time Sunday.

Higashioka, who turns 27 on April 20, was known inside the organization as a defensive catcher until last year, when he combined for 22 homers and 81 RBIs between Double-A Trenton and SWB.

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“It feels like I made the right decision to stay,’’ said Higashioka, who could have left as a six-year minor league free agent and was dropped from the 40-man roster following the 2015 season. “It’s nice to make it up with the organization you started with.’’

Higashioka was eating dinner at Bravo in Buffalo when SWB manager Al Pedrique told him he was going to the big leagues. A six-hour drive got Higashioka and his wife, Alyse, to Camden Yards.

If Sanchez is gone for an extended stretch, the trade market for catchers is thin, and a scout said Sunday a combination of “Romine and Higgy is the best option.’’

The best outside of the organization might be the Padres’ Hector Sanchez, who is on the seven-day concussion list. He has played in 275 big-league games and had a good spring training with the bat. Other possibilities include Tampa Bay’s Jesus Sucre and the Mariners’ Tuffy Gosewisch, a 33-year-old with 126 games in the big leagues currently catching at Triple-A Tacoma.

There is also former Yankee John Ryan Murphy, who is in Triple-A with the Twins, and Ryan Hanigan, who was released by the Phillies in spring training and is playing for Albuquerque, the Rockies’ Triple-A club. Bobby Wilson with the Dodgers’ Triple-A team in Oklahoma City and the Brewers’ Manny Pina may become available.